Stabilized Laser Source with Very High Relative Feedback and Narrow Bandwidth

Abstract

This invention relates to the stabilization of a laser source used in optoelectronics, specifically a source comprising a semiconductor laser diode (1). Such laser sources are often used as so-called pump lasers for fiber amplifiers in the field of optical communication, erbium-doped fiber amplifiers being a prominent example. Such lasers are usually designed to provide a narrow bandwidth optical radiation with a stable power output in a given frequency band. The present invention now concerns such a laser source using external reflector means, preferably consisting of one or more appropriately designed fiber Bragg gratings (9), providing very high relative feedback with an extremely narrow bandwidth, combined with a very long external cavity encompassing about 100 modes or more and an extremely low front facet (2) reflectivity of the laser diode. This stabilizes the laser source extremely well in its operation, without the need for an active temperature stabilizing element.

Description

FIELD OF THE INVENTION[0001]This invention relates to the stabilization of a laser source, specifically a semiconductor laser diode of the type commonly used in opto-electronics, mostly as so-called pump lasers for fiber amplifiers in the field of optical communication. Erbium-doped fiber amplifiers are a prominent example using such laser diodes. Usually, such laser sources are designed to provide a relatively narrow-bandwidth optical radiation with a stable power output in a given frequency band. In particular, the invention relates to a laser using external reflector means providing very high relative feedback with a narrower bandwidth compared to conventional devices and in addition extremely low noise operation, even without an active temperature stabilizing element. Another advantage of the invention is the reduction of spectral distortions, in the case that polarization maintaining fiber is used. Such a laser source can also be used in different applications like frequency do...

AI Technical Summary

Benefits of technology

[0001]This invention relates to the stabilization of a laser source, specifically a semiconductor laser diode of the type commonly used in opto-electronics, mostly as so-called pump lasers for fiber amplifiers in the field of optical communication. Erbium-doped fiber amplifiers are a prominent example using such laser diodes. Usually, such laser sources are designed to provide a relatively narrow-bandwidth optical radiation with a stable power output in a given frequency band. In particular, the invention relates to a laser using external reflector means providing very high relative feedback with a narrower bandwidth compared to conventional devices and in addition extremely low noise operation, even without an active temperature stabilizing element. Another advantage of the invention is the reduction of spectral distortions, in the case that polarization maintaining fiber is used. Such a laser source can also be used in different applications like frequency doubling systems, where effectiveness depends critically on a narrow spectral range and where noise requirements are stringent.

Problems solved by technology

One of the problems occurring when using semiconductor laser diodes for the above purpose is their wavelength and power output instability which, though small, still affects the amplification sufficiently that there is motivation to look for a solution to the problem.

Additionally, low-frequency power fluctuations seem to decrease by the effect of induced high-frequency multi-mode operation.

None of the above prior art addresses solutions for high power (i.e. >100 mW) laser sources, capable of stable operation without using an active temperature stabilizing element.

The need for TEC's contributes significantly to the complexity and cost of a laser source.

A less known and undiscussed problem is that of spectral distortions which may occur when a polarization-maintaining fiber is used for typical laser-grating configurations in fiber amplifier systems.

However, slight residual reflections act as small pertubations to the dominant mode field, influencing—and sometimes deteriorating—the performance of the laser source.

Images